Process of electrolytical extraction of metals.



No. 669,926. Patented Mar. l2, I90l.

C. HOEPFNER. v PROCESS OF ELEBTBOL YTICAL EXTRACTION 0F METALS.

(Application filed Sept. 27, 1899.)

(No Model.)

.Nrrr; STATES PATENT OFFicE.

CARL l-IOEPFNER, OF FRANKFORT-ONTHE-MAIN, GERMANY.

PRooEss OF ELECTROLYTICAL EXTRACTION 0F METALS.

SPECIFICATION forming part of Letters Patent No. 669. dated March 1901- Application filed eptember 27, 1399. Serial No. 731,854. (No specimens.)

To 00% whom 21!; may concern.-

Be it known that I, CARL I-IOEPFNER, a subject of the Emperor of Germany, residing atv Frankfort-ol'l-the-Main, Germany, have in vented certain newand useful Improvements in Processes of Electrolytical Extraction of Metals; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawing, and to letters of reference marked thereon, which forms a part of this specification.

This invention relates to the electrolytic process for the extraction of metals where a metallic anode insoluble in'dilute acids and less electropositive tlianzinc is used and a me tallic cathode which is of the metal to be deposited, but different from the anode metal.

I employ electrolytes separated by two diaphragms into anode and cathode cells, and between these two is a solution designed to prevent the bad effect of diffusion from the anode to the cathode electrolyte. The metal dissolving in the anode-cell differs from that in the cathode-cell, is precipitable by metallic zinc and preferably, also, by a compound or salt of the metal in the, cathode solution. The electrolytes are preferably, but not necessarily, caused to circulate through a series of cells and, if desirable, also the solutions in the intermediate cells. Means are provided for heating one or all the solutions employed.

Any suit-able apparatus that will accomplish the results may be used.

In the apparatus shown partly in section in the accompanying drawing, A represents the anodes, and C the cathodes, each in their respective compartments a and c, which are formed by a number of frames g, between which are clamped the diaphragms d, that separate the cells a and c and the intermediate compartments 6. Into the intermediate compartments or cells I preferably suspend a second cathode B, which is conveniently made in the form of a tubular coil, so as to permit the heating of the solution by steam. This auxiliary cathode must not be so formed as to make a solid wall, or it will arrest all the current, and so prevent electrolysis in the adjoining catl1ode-cell.

odes. metal is then either sold or reduced by car- 8 is the passage between the anode-cells,

and ff the passages between the cathodecells, formed in the vertical members of the frames g, which allow of the circulation of the electrolytes through each series or sets of compartmen ts. The intermediate cells I) may also be conn ected in series to allow the electrolytes to circulate from one to the other, although they are preferably connected in parallel.

The frames g are clamped between suitable heads by means of rods E and clam in -bars F.

All the electrodes are shown suspended from a frame X,to which vibration is imparted by suitable mechanism, here shown as an cecentric.

The electrolytes are preferably, but not necessarily, preheated in any suitable manner, and it is well that they then be kept. warm by passing steam through the tubular coil in the intermediate cells.

As it is of great advantage to maintain the cathode solution in constant motion, the cathodes, and preferably the anodes and the auxiliary cathodes also, are kept vibrating, while the electrolyte should be kept circulating from an appropriate reservoir through the cells.

The soluble anodes are composed of metals not soluble in dilute sulfuric acid,(thus excluding iron and zinc,) and care must be taken not to allow the anode solutions to reach the cathodes.

The metals dissolved from the anodes are bon or other solid or gaseous reducing agents to a metallic state or otherwise utilized.

For the sake of clearness in the rest of the specification I shall take lead as an example of the anode metal and zinc as of the cathode metal, but wish to make it clear that other metals, especially copper, can replace the lead as an anode metal. Thus I use lead or materials containing lead, such as sulfid of lead or argentiferous lead, for anodes. These substances are I cast into plates, grids, or bars or simply placed in a suitable wire casing in a powdered or granulated condition. In the latter case electronegative metals such as gun-metal, copper-bronze, silver-wire netting, or carbon rods, or the likemay.be used for carrying the current to and for containing the anode material. It will be well to also keep the anode solution in motion, especially when using powdered sulfids.

The solution around the anodes is an acid or neutral salt solution, preferably heated, and its nature should be such as to readily dissolve the compounds of lead formed at the anodes. The agents most suitable for this purpose are solutions of chloridsespeciall v sodium chlorid, chlorid of zinc, or chlorid of potassiumnitrates or nitrit-es, as nitrates of sodium and zinc, acetates of sodium and zinc, and other acids and salts capable of forming soluble compounds of lead or of copper or other metals.

In order to have a continuously-working process, the anode-electrolyte should not be allowed to absorb too much lead, in no case more than from fifty to one hundred grams per liter, because if the quantity were larger it would cause an undue rise of voltage, and

the lead and other metals of the anode would be liable to diffuse into the cathode solution and impair the purity of the zinc. To this end the electrolyte is in constant circulation through the anode-cells, and in the course of its travel the lead is precipitated, preferably outside of the anode-cells, by means of a compound of a cathode metal, in this case a zinc compound, any one of the following being, according to circumstances, more or less suitable: zinc sulfate, (ZnSO zinc chromate, (ZnCrO zinc sulfite, (ZnSO zinc carbonate, (ZnOO zinc silicate, (ZnSiO zinc oxid, (ZnO,) zinc sulfid, (ZnS,) and, at reduced temperatures, zinc chlorid (Zn 01 or basic carbonate of zinc. By means of any one of these compounds the lead will be precipitated from the chlorid, nitrate, or acetate solutions, and the resulting electrolyte will practically only contain zinc and may go back to the anodes or will when purified by zincdust be fit for use as a cathode-electrolyte from which zinc is to be deposited, the reactions taking place as follows:

ZnR-l-PbR PbR+7mR insoluble.

By means of pure oXid of zinc and carbonic acid white lead may be obtained.

It is obvious that for the precipitation of lead or copper other harmless reagents may be used in conjunction therewith-such as alkali or alkaline earth chlorids, bromids, chromates, sulfates, sulfites, sulfids, sulfureted hydrogen, ammonia,the alkaline earths themselves, carbonates, and sometimes acids such as sulfurous, sulfuric, or carbonicand,

finally, compounds of leadas.oxid, carbon ate, or hydroxidor roast-ed lead ores, which form a nearly insoluble basic compound with the salt of lead in the anode solution. Where an inexpensive source of heat is available, the

I dissolved salt of lead may also be precipitated physically by cooling or by diluting the solution.

In order to securely prevent the precipitation of any diffused lead on the cathode, sulfates or other substances capable of rendering the lead more insoluble before reaching the cathodes may be added to the cathode and intermediate solutions; but as a more reliable safeguard against any diffusion of the lead to the cathodes I use, as shown, a third or intermediate cell which conlains a solution preferably similar to those in the other two cells, by which I mean that if an acetic-acid solution is used in the anode and cathode cells it is advisable to use such a solution in the intermediate cell, although not absolutely necessary. This intermediate solution can be kept practically free from anode metal in one way or another, and in order to prevent the diffusion of the anode solution (which is constantly varying in density by reason of the dissolution of the anode metal) to the cathodecell, in which also the density of the cathode solution is constantly varying by reason of the deposition of cathode metal, I prefer to maintain a hydrostatic pressure in the several cells in the direction from the cathode to the anode, such that this varying pressure will practically counteract the tendency to diffusion from the anode to the cathode, and this I accomplish by maintaining in the oathode-compartments the greatest hydrostatic head, in the intermediate compartments a less head, and in the anode-compartments the least, so that the bulk of diffusion is toward the anodes. In this intermediate cell I may also place a second cathode of zinc, lead, copper, or aluminium of any desirable shape, preferably kept in vibration, and have shown this cathode B as a tubular lead coil allowing the free passage of current from the anode to the cathode and also capable of beingheated by steam. These coils are then connected with the cathode by a wire of high resistance, the diffused lead being deposited on them. Thus the intermediate solution can be kept free from'lead (or copper) either chemically, (by suit-able precipitants,) physically, or electrolytically. After all lead has been removed from this intermediate solution it. can be combined with the anode solution, also freed from lead, and when sufficiently enriched in zinc can be used as the cathode solution. It is convenient in most cases to add alkaline salts or salts of alkaline earths to all three solutions or any one of them to render them more conductive.

Lead and copper anodes are extremely economical in this process, as they require but a low voltage to transform them into their salts in the anode-cell, thus allowing of the production of thirty pounds of zinc per day. Besides, their precipitates allow of a very econominal reduction to metal by heat or other reducing agents.

When a copper anode is used, the dissolved metal may be conveniently precipitated, as an oxychlorid, subchlorid, or snlfid. In a similar way by using the described intermediate cells and anodes of lead or copper it is possible to produce from alkaline salts their amalgams, or, after combination with the water present, hydrogen and hydroxids, or,with the addition of CO carbonates. Then in those alkaline solutions surrounding the oathodes oxids of metal, as lead or zinc, can be dissolved and be decomposed electrolytically, thereby producing metallic zinc or lead as a by-product instead of hydrogen; In that case the anode solution is freed from its anode metal, preferably by a compound of an alkali i. a, lead may be precipitated from a nitrate solution by a sulfate or chlorid of an alkali or physically by cooling. The copper may then be precipitated as cuprous chlorid or oxychlorid by sodium chlorid and metallic copper, or sulfid of copper or other suitable reagents or sulfids, or by the action of air.

Having thus described my invention, What I claim new therein, and desire to secure by Letters Patent, is-

1. A process which consists in. placing a solublenietallic anode other than iron or zinc in a solution of a salt capableiof dissolving the same, placinga suitable cathode in asecond solution containing a metal other than that contained in the anode, interposing a third solution between the two first mentioned, separating the solutions by means of suitable diaphragms, passingacurrent,thereby bringing the anode metal into solution and depositing the cathode metal, precipitating the anode metal from the anode solution onriching it in cathode metal and conveying the resulting solution to the cathode-compartment, substantially as set forth.

2. A process which consistsin placinga suitable metallic anode in a solution of a salt capable of dissolving the same, placing a suitable cathode in a second solution containing a metal other than that contained in the anode, interposing a third solution having a less solutionpressu re than the cathode-electrolyte, separating the solutions by suitable diaphragms, passingacurrent, thereby bringing the anode metal into solution and depositing the cathode metal, precipitating the anode metal from the anode solution by means of a cathode-metal compound and conveying the resulting solution to the cathode -compartment, substantially as set forth.

3. A process which consists in placing a metallic anode other than zinc or iron in a solution capable of dissolving the same, placing a suitable cathode in a solution similar to that at the anode, containing however no metal more electronegative than zinc, but containing also zinc, interposing a third solution having a less solution-pressu re than that at the cathode, between the two first mentioned, separating the solutions by means of suitable diaphragms, passingacurrent, thereby bringing the anode metal into solution and depositing zinc at the cathode, preci pitati ngthe anode metal by means of a zinc com pound, convey: ing the resulting solution to the cathode-compartment and removing the diffused anode metal from the intermediate solution, substantially as set forth.

4. A process, which consists in placing a lead or copper anode in a solution capable of dissolving the same, placing a suitable cathode in a solution similar to that at the anode but containing also zinc, containing however no metal more electronegative than zinc, interposing a third solution of less solutionpressure than the cathode solution and adapted to prevent diffusion of anode into the oathode solution, separating the solutions by suitable diaphragms, passing a current, thereby bringing lead or copper into solution and depositing zinc at the cathode, precipitating the lead or copper dissolved in the anode solution by adding a zinc compound thereto and conveying the resulting solution to the oathode-compartment, substantially as set forth.

5. A process, which consists in placing a lead or copper anode in a solution capable of dissolving the same, placing a suitable cathode in a solution similar to that at the anode.

but containing also zinc, containing however no metal more electronegative than zinc, interposing a third similar solution between the aforesaid solutions and separating them by suitable diaphragms, maintaining the temperature of the solutions above normal, passlead or copper anode in a solution capable of dissolving the same, placing a suitable cathode in a solution similar to that at the anode but containing also zinc, containing however no metal more eleotronegative than zinc, interposing a third similar solution between the aforesaid solutions and separating them by suitable diaphragms, maintaining their temperature above normal, passing a current from the anode through both solutions to the cathode, thereby bringing the lead or copper into solution at the anode and depositing zinc at the cathode, precipitating the lead by means of zinc carbonate outside the cells and conveying the resulting solution to the cathode-cell,-substantially as set forth.

7. A process which consists in placing a lead or copper anode in a solution capable of dissolving the same, placing a suitable cat-hode in a solution similar to that at the anode but containing also zinc, containing however no metal more electronegative than zinc, interposing a similar third solution of less solution-pressure than that at the cathode, separating the solutions by suitable diaphragms, maintaining their temperature above normal, passing a current from the anode through the solutions to the cathode, thereby bringing the lead or copper into solution at the anode and depositing zinc at the cathode, precipitating the lead from the anode and intermediate solution by means of zinc oxid and carbonic acid and conveying the resulting solution to the cathode-cells, substantially as set forth.

8. A process which consists in placing a lead or copper anode in a solution capable of dissolving the same, placing a suitable cathode in a solution similar to that at the anode but containing also zinc, containing however no metal more electronegative than zinc, interposing a third similar solution designed to prevent the diffusion of the anode solution into the cathode solution, and placing an auxiliary cathode therein, separating the solutions by suitable diaphragms, maintaining their temperature above normal, passing a current from the anode through the solutions to the cathodes, thereby bringing the lead or copper into solution at the anode and depositing zinc at the cathode and the diffused lead at the auxiliary cathode, precipitating the lead or copper from the anode solution, treating the raw material containing zinc with the said solution and conveying the resulting solution to the cathode-cell, substantially as set forth.

9. A process, which consists in placing a soluble metallic anode in a solution of a salt capable of dissolving the same, placing a suitable cathode ina second solution containing a metal other than that of the anode, interposing a third solution between the two first mentioned, separating the solutions by suitable diaphragms, passing a current, thereby bringing the anode metal into solution and depositing the cathode metal, precipitating the anode metal from the anode solution and likewise that diffused into the intermediate solution, enriching the resulting anode solution in zinc and returning it to the cathodecells.

10. A process which consists in placing a soluble metallic anode in a solution of a salt capable of dissolving the same, placing a suitable cathode in a second similar solution containing a metal other than that of the anode, interposing a third solution of less solutionpressure than the first mentioned, placing a suitable auxiliary cathode therein, separating the solutions by suitable diaphragms, maintaining all the solutions in motion and at a temperature above normal, passinga current, thereby bringing the anode into solution and depositing the cathode metal at the cathode and the diffused anode metal at the auxiliary cathode, precipitating the anode metal from the anode solution enriching the resulting solution in cathode metal and conveying it to the cathode-compartment, substantially as set forth.

11. A process which consists in placing a soluble metallic anode in a solution capable of dissolving the same, placing a suitable cathode in a second similar solution containing a metal more 'electropositive than that of the anode, interposing a third similar solution of less solution-pressure between the two first mentioned, placing an auxiliary cathode therein, separating the solutions by suitable diaphragms, maintaining the solutions in motion and at a temperature above normal, passing a current, thereby dissolving the anode and precipitating .the cathode metal at thecathode and part of the difl'used anode metal at the auxiliary cathode, precipitating the anode metal from the anode and intermediate solutions and returning the resulting solution when enriched in cathode metal to the cathode-cell, substantially as set forth.

12. A process, which consists in placing a soluble anode of lead or copper in a solution of a salt capable of dissolving the same, placing a suitable cathode in a second solution containing a metal of the alkalies and an oxygen compound of a metal soluble in alkalimetal solutions, interposing a third solution between the two first mentioned, separating the solutions by suitable diaphragms, passinga current, thereby bringing the anode metal into solution, depositing the cathode metal and forming an alkali hydroxid, substantially as set forth.

In testimony that I claim the foregoing as my invention I have signed my name in presence of two subscribing witnesses.

CARL HonPFNER.

Witnesses:

Tnos. I-I. YOUNG, B. W. SoMMERs. 

